During a posterior cervical stabilization procedure the surgeon generally places screws into the lateral mass of the cervical vertebral body followed by a titanium rod and set screws. The described posterior cervical stabilization procedure provides stabilization of the cervical spine to aid in fusion of one or more levels of the spine. One end section of the rod is occasionally anchored to a plate attached to the occipital region in a procedure called occipitocervical stabilization. In occipitocervical stabilization constructs, the rod is characterized by two sections—a first section that extends over the cervical spine and a second section that connects to the occipital plate at an angle relative to the first section.
In conventional occipitocervical fixation assemblies, the rod may be pre-bent before placement in the patient to form the angle between the first and second sections. Once the rod is bent it may be used to connect a screw or hook at a cervical vertebrae and an occipital plate. The screw or hook may be placed at C1, C2, C3 or any level caudally. Each rod must be customized for each patient's unique anatomy, thus one rod configuration may not be used for all patients. A number of variables vary from patient to patient including the angle between the first and second rod sections. Since each patient's anatomy varies a pre-bent rod may not match each patient's anatomy precisely when the rod is placed. Further adjustment of the pre-bent rod is therefore regularly required during placement of the fixation assembly and is generally performed intraoperatively.
Adjusting a rod prior to and/or during an operation can create stress on the rod which decreases the fatigue strength of the rod material. If the fatigue strength is reduced significantly, then the integrity of the rod can be compromised and pose a significant risk to the patient. In addition, it may be time consuming and cumbersome to bend a rod prior to or during an operation. The rod bending problems are experienced with occipitocervical fixation assemblies, as well as other spinal inflection points such as lumbopelvic spine fixation assemblies and other implant systems featuring elongated elements that are manually configured to conform to specific spatial requirements.